Pattern generation  device

ABSTRACT

One embodiment of the invention provides a pattern generation device includes a light source, a first HPDLC cell, and a second HPDLC cell. The first HPDLC cell is disposed downstream of a light path of the light source and contains a first phase modulation pattern. The second HPDLC cell is disposed downstream of a light path of the first HPDLC cell and contains a second phase modulation pattern.

BACKGROUND OF THE INVENTION a. Field of the Invention

The invention relates to a pattern generation device.

b. Description of the Related Art

Nowadays, encoded or structured light is considered to be a reliabletechnology for purposes of mapping surface contours of objects. In atypical structured-light 3D scanning process, specific patterns areprojected onto an object or a scene, and the projected patterns are thencaptured by an image pick-up device from one or more perspectives. Thestructured light patterns may be composed of lines, grids or morecomplicated geometric shapes. Because structured light patterns havebeen encoded, positional relationships between reference points andprojection points in the captured image can be easily found out.Therefore, the depth coordinate of each point can be found bytriangulation based on the local shift to reconstruct athree-dimensional (3D) map of an object. This 3D mapping techniquerelying on structured light can be used in various applications, such asdepth measurements, distance measurements, component inspection, reverseengineering, gesture recognition, and creation of three dimensionalmaps.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present disclosure, a pattern generation deviceincludes a light source, a first holographic polymer dispersed liquidcrystal (HPDLC) cell, and a second HPDLC cell. The first HPDLC cell isdisposed downstream of a light path of the light source and contains afirst phase modulation pattern. The second HPDLC cell is disposeddownstream of the light path of the first HPDLC cell and contains asecond phase modulation pattern. A power supply is electricallyconnected to the first HPDLC cell and the second HPDLC cell and suppliesa voltage to one of the first HPDLC cell and the second HPDLC cell. Alight beam from the light source and travelling through the first HPDLCcell is converted into an image beam with a first image pattern incorrespondence with the first phase modulation pattern. Alternatively, alight beam from the light source and travelling through the second HPDLCcell is converted into an image beam with a second image pattern incorrespondence with the second phase modulation pattern. Finally, theimage beam is projected onto an object.

In another aspect of the present disclosure, a pattern generation deviceincludes a light source, a first grating, a second grating, and aholographic optical element. The first grating is switchable between anon-diffracting and a diffracting state and disposed downstream of alight path of the light source, and the second grating is switchablebetween a non-diffracting and a diffracting state and disposeddownstream of a light path of the first grating. The holographic opticalelement is disposed downstream of a light path of the second grating,and the holographic optical element encodes a first phase modulationpattern in correspondence with a first image pattern and a second phasemodulation pattern in correspondence with a second image pattern. Apower supply is electrically connected to the first grating and thesecond grating and supplies a voltage to one of the first grating andthe second grating. A light beam from the light source travels throughthe first grating and the second grating. The light beam incident to thefirst grating is converted into an image beam with a first image patternand deflected by the first grating at a first angle, and the light beamincident to the second grating is converted into an image beam with asecond image pattern and deflected by the second grating at a secondangle. Finally, the image beam is projected onto an object.

In another aspect of the present disclosure, a pattern generation deviceincludes a light source, a light valve, a first grating, a secondgrating and a projection lens. The light valve contains a pattern and isdisposed downstream of a light path of the light source. The firstgrating is switchable between a non-diffracting and a diffracting stateand disposed downstream of a light path of the light valve. The secondgrating is switchable between a non-diffracting and a diffracting stateand disposed downstream of a light path of the first grating. Aprojection lens is disposed downstream of a light path of the secondgrating. A power supply is electrically connected to the first gratingand the second grating and supplies a voltage to one of the firstgrating and the second grating. A light beam from the light source isconverted by the light valve into an image beam with an image pattern.The image beam is bent by the first grating at a first angle or bent bythe second grating at the second angle, and the image beam is finallyprojected onto an object by the projection lens.

According to the above aspects, a pattern generation device having lowpower dissipation and low fabrication costs is provided, and the patterngeneration device may provide periodic patterns and more collimatablelight beams to expand applications of structured light.

Other objectives, features and advantages of the invention will befurther understood from the further technological features disclosed bythe embodiments of the invention wherein there are shown and describedpreferred embodiments of this invention, simply by way of illustrationof modes best suited to carry out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a depth mapping system according toan embodiment of the invention.

FIG. 2 shows a schematic diagram of a pattern generation deviceaccording to an embodiment of the invention.

FIG. 3A and FIG. 3B respectively show a cross-sectional view and aperspective view of a holographic polymer dispersed liquid crystal(HPDLC) cell.

FIG. 4A shows a cross-section of a HPDLC cell supplied with a voltageand FIG. 4B shows a cross-section of the HPDLC cell not supplied with avoltage.

FIG. 5 shows a schematic diagram of an image pattern projected on anobject by a pattern generation device according to an embodiment of theinvention.

FIGS. 6A and 6B show schematic diagrams of a pattern generation deviceunder different operating conditions according to another embodiment ofthe invention.

FIG. 6C shows a schematic diagram of different image patterns projectedon an object by a pattern generation device according to an embodimentof the invention.

FIG. 6D shows a schematic diagram of different image patterns projectedon a hand by a pattern generation device according to an embodiment ofthe invention.

FIGS. 7A and 7B show schematic diagrams of a pattern generation deviceunder different operating conditions according to another embodiment ofthe invention.

FIG. 8 shows a schematic diagram of a pattern generation deviceaccording to another embodiment of the invention.

FIGS. 9A and 9B show schematic diagrams of a pattern generation deviceaccording to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments,directional terminology, such as “top,” “bottom,” “front,” “back,”etcetera, is used with reference to the orientation of the Figure(s)being described. The components of the invention can be positioned in anumber of different orientations. As such, the directional terminologyis used for purposes of illustration and is in no way limiting. Further,“First,” “Second,” etcetera, as used herein, are used as labels fornouns that they precede, and do not imply any type of ordering (e.g.,spatial, temporal, logical, etcetera).

FIG. 1 shows a schematic diagram of a depth mapping system. Referring toFIG. 1, a depth mapping system 100 includes a pattern generation device110 and an image pick-up device 120. The depth mapping system 100measures depth coordinate values of the surface of an object 130 at eachpoint within a predefined field of view, where the pattern generationdevice 110 projects a structured light pattern or modulated pattern ontothe object surface and the image pick-up device 120 captures an image ofthe structured light pattern on the object surface to obtain the depthcoordinate values. Specifically, the pattern generation device 110 isused to project a light beam L of encoded/structured light onto thesurface of the object 130. The depth mapping system 100 may furtherinclude a calculation unit 140. The calculation unit 140 is electricallyconnected to the image pick-up device 120 to find a depth map of theobject 130 according to an image of the light beam L on the objectsurface captured by the image pick-up device 120. For example, the depthmap of the object 130 is generated by decoding the light beam L and bythe triangulation approach. The image pick-up device 120 may be a devicewith a CCD or a CMOS, such as a camera, a mobile phone, or a portabledevice. The calculation unit 140 may be an operational processor such asa CPU, an MCU, a DSP, an MPU, an FPGA or a GPU.

FIG. 2 shows a schematic diagram of a pattern generation device 110according to an embodiment of the invention. FIG. 3A and FIG. 3Brespectively show a cross-sectional view and a perspective view of aholographic polymer dispersed liquid crystal (HPDLC) cell. In oneembodiment, a HPDLC cell 210 is a grating switchable between adiffracting state and a non-diffracting state. As shown in FIG. 2, thepattern generation device 110 includes a light source 200, multipleHPDLC cells 210 (such as HPDLC cells 210 a-210 c), a power supply 220and multiple switches 230. In one embodiment, the power supply 220supplies a voltage signal to the HPDLC cells 210. In other embodiment,the power supply 220 supplies a current signal to the HPDLC cells 210. Alight beam L emitted from the light source 200 passes through the HPDLCcells 210 and reaches the surface of the object 130. Further, bycontrolling respective on/off states of the multiple switches 230, thepower supply 220 may selectively supply or not supply a voltage signalto the HPDLC cells 210 a-210 c. The light source 200 may be asingle-point type, a multipoint type or a surface type light source, andthe light source 200 may include, but is not limited to, a laser, alaser diode, an LED, an OLED, a vertical-cavity surface-emitting laser(VCSEL), an edge-emitting laser, a bulb, or a light-emitting unitcapable of emitting thermal-spectrum radiation (such as infrared lightor other invisible light).

Referring to FIG. 3A and FIG. 3B, an HPDLC cell 210 includes a top glass(or plastic) substrate 211, a bottom glass substrate 212, transparentelectrodes 213 and 214, a HPDLC layer 216 and multiple beads 219. Thetop glass substrate 211 and the bottom glass substrate 212 are spaced atan interval, and the transparent electrodes 213 and 214 are respectivelydisposed on inner surfaces of the glass substrates 211 and 212. TheHPDLC layer 216 is disposed between the transparent electrode 213 andthe transparent electrode 214 and is composed of polymers 217 and liquidcrystals 218. The light beam L from the light source 200 may passvarious HPDLC cells 210 along a propagation path determined by whetherrespective HPDLC cells 210 are supplied with a voltage or current and byprescribed patterns defined by polymers 217 and liquid crystals 218. Thedifferent refractive indices of polymers 217 and liquid crystals 218 maycause light diffraction effects. The beads 219 are disposed between thetransparent electrode 213 and the transparent electrode 214 to maintaina thickness of the HPDLC layer 216. The beads 219 are not limited tohaving a specific number. For example, each of the top side and thebottom side of the HPDLC layer 216 is preferably provided with at leasttwo beads. In one embodiment, the transparent electrodes 213 and 214 areformed from indium tin oxide (ITO) conductive films.

FIG. 4A and FIG. 4B show a HPDLC cell functioning as a gratingswitchable between a diffracting state and a non-diffracting state,where FIG. 4A shows a cross-section of a HPDLC cell supplied with avoltage and FIG. 49 shows a cross-section of the HPDLC cell not suppliedwith a voltage. When a voltage is applied to the HPDLC cell (grating)210 switchable between a diffracting state and a non-diffracting state,molecules of liquid crystals 218 are oriented according to a prescribedpattern as shown in FIG. 4A. Therefore, the refractive index of liquidcrystals 218 is substantially the same as that of polymers 217, and alight beam L from the light source 200 may, when reaching the HPDLC cell(grating) 210, travel though molecules of liquid crystals 218 in analmost straight direction without being subject to optical interference.In one embodiment, the transmittance of the light beam L may reach 98%or above. In comparison, when no voltage is applied to the HPDLC cell(grating) 210 switchable between a diffracting state and anon-diffracting state, molecules of liquid crystals 218 are orientedaccording to another prescribed pattern as shown in FIG. 49. Therefore,the different refractive indices of polymers 217 and liquid crystals 218result in light diffraction effects, and thus the light beam L incidentto the HPDLC cell 210 is subject to optical diffraction to exit theHPDLC cell 210 in a direction different to the incident direction; thatis, the light beam L is deflected by the HPDLC cell 210 as shown in FIG.49. Except for serving as a grating switchable between a diffractingstate and a non-diffracting state to vary the light exit direction, theHPDLC cell 210 may also contain phase modulation informationcorresponding to an image pattern to be projected on the object surface.In one fabrication example, polymers 217 outsides a phase modulationpattern region is exposed to a light beam to be cured. Therefore, liquidcrystals 218, which have a certain degree of fluid property, is pushedby the curing polymers 217 in the HPDLC layer 216 and flow into thephase modulation pattern region. Therefore, when no voltage is appliedto the HPDLC cell 210 and a light beam L is incident to the HPDLC cell210 containing a phase modulation pattern, an image pattern correspondsto the phase modulation pattern is displayed on the object 130.Referring to FIG. 5, in one embodiment, a voltage is applied to HPDLCcells 210 a and 210 c but not applied to a HPDLC cell 210 b by controlsof multiple switches 230. Therefore, a light beam L from the lightsource 200 passes through the HPDLC cell 210 a and the HPDLC cell 210 bin succession (i.e., the HPDLC cell 210 b is disposed downstream of alight path of the HPDLC cell 210 a) and is converted relying on a phasemodulation pattern 242 of the HPDLC cell 210 b into an image beam with apattern 240 that corresponds to the phase modulation pattern 242. Then,the image beam with the pattern 240 passes through the HPDLC cell 210 cwithout any modification or conversion to display the pattern 240 on thesurface of the object 130.

FIG. 6A and FIG. 6B illustrate a pattern generation device 310 accordingto another embodiment of the invention. In FIG. 6A and FIG. 6B,identical components are denoted by the same numerals as in the aboveembodiments and their descriptions provided above will not be repeatedhere. In this embodiment, each HPDLC cell 210 is a grating switchablebetween a diffracting state and a non-diffracting state to alter theexit angle of the light beam L, and the HPDLC cells 210 are used with aholographic optical element 250, such as a hologram, that generatesdifferent holographic images as a result of different angles ofincidence of a light beam impinging thereon. FIG. 6A illustrates acondition where a voltage is applied to the HPDLC cells 210 a and 210 cbut not applied to the HPDLC cell 210 b by controls of multiple switches230. As shown in FIG. 6A, a light beam L from a light source 200 passesthrough the HPDLC cell 210 a in a substantially straight direction andis incident to the HPDLC cell 210 b. The light beam L is deflected bythe HPDLC cell 210 b at an angle α1 and then incident to the HPDLC cell210 c. Then, the light beam L passes through the HPDLC cell 210 c in asubstantially straight direction and is incident to the holographicoptical element 250 (such as a hologram) to display an image pattern 260on the object 130 (shown in FIG. 6C) by the holographic optical element250 encoding a phase modulation pattern (not shown) corresponding to theimage pattern 260. FIG. 6B illustrates a condition where a voltage isapplied to the HPDLC cell 210 a and HPDLC cell 210 b but not applied tothe HPDLC cell 210 c by controls of multiple switches 230. As shown inFIG. 6B, a light beam L from the light source 200 passing through theHPDLC cell 210 a and HPDLC cell 210 b in a substantially straightdirection is incident to the HPDLC cell 210 c. The light beam L isdeflected by the HPDLC cell 210 c at an angle α2 and then incident tothe holographic optical element 250 (such as a hologram) to display animage pattern 270 on the object 130 (FIG. 6C) by the holographic opticalelement 250 encoding a phase modulation pattern (not shown)corresponding to the image pattern 270. Note that the phase modulationpattern is an interference pattern that enables a device to reproducethe original light field and finally form an image pattern. Therefore,the image patterns 260 and 270 projected on the surface of the object130 are different to the phase modulation pattern of the holographicoptical element 250.

As shown in FIG. 6D, in one embodiment, the object 130 is a hand, andthe hand gesture may cause distance differences between differentsurface tiles of a hand and an image pick-up device 120. The imagepick-up device 120 may capture an image of the hand and thus fetch imagepatterns 260 and 270 on the object (hand) 130. Therefore, a differentdepth of each tile of the hand is obtained by detecting positionalrelationships between the image pattern 260 and the image pattern 270.Note the resolution of each tile of the hand is determined by the styleof the image patterns 260 and 270. For example, a smaller pitch amongline patterns and/or point patterns may increase the resolution of eachtile. Further, the pattern described in various embodiments of theinvention is not limited to a specific style or construction. Forexample, the pattern may include multiple strips of equal width or withdifferent widths and may have irregular, periodic, point or linearshapes.

FIG. 7A and FIG. 7B illustrate a pattern generation device 410 accordingto another embodiment of the invention. In FIG. 7A and FIG. 7B,identical components are denoted by the same numerals as in the aboveembodiments and their descriptions provided above will not be repeatedhere. In this embodiment, each HPDLC cell 210 is a grating switchablebetween a diffracting state and a non-diffracting state to alter theexit angle of the light beam L, and the HPDLC cells 210 is used with aprojection lens 290 and a transparent substrate 280 containing a pattern(not shown). The projection lens 290 is disposed downstream of a lightpath of the gratings. FIG. 7A illustrates a condition where a voltage isapplied to the HPDLC cell 210 a and HPDLC cell 210 c but not applied tothe HPDLC cell 210 b by controls of multiple switches 230. As shown inFIG. 7A, a light beam L from a light source 200 first passes through thetransparent substrate 280 containing a pattern (not shown) in asubstantially straight direction to be converted into an image beam withthe pattern. Then, the image beam with the pattern passes through theHPDLC cell 210 a and reaches the HPDLC cell 210 b in a substantiallystraight direction, and is deflected by the HPDLC cell 210 b at an angleα1 and then incident to the HPDLC cell 210 c. Thereafter, the image beamwith the pattern passes through the HPDLC cell 210 c in a substantiallystraight direction and projected by the projection lens 290 to displaythe pattern of the transparent substrate 280 on the object 130. FIG. 7Billustrates a condition where a voltage is applied to the HPDLC cell 210a and HPDLC cell 210 b but not applied to a HPDLC cell 210 c by controlsof multiple switches 230. As shown in FIG. 7B, a light beam L from alight source 200 first passes through the transparent substrate 280provided with a pattern (not shown) in a substantially straightdirection to be converted into an image beam with a pattern, and thenthe image beam with the pattern passes through the HPDLC cell 210 a andthe HPDLC cell 210 b in succession in a substantially straight directionand reaches the HPDLC cell 210 c. The image beam with the pattern isdeflected by the HPDLC cell 210 c at an angle α2 and projected by theprojection lens 290 to display the pattern of the transparent substrate280 on the object 130. Though FIG. 7A and FIG. 7B both show that anidentical pattern of the transparent substrate 280 is displayed on theobject 130, the mutually different deflection angles α1 and α2 may causea displacement between two identical patterns. Therefore, the image ofthe object 130 captured by the image pick-up device 120 may include twoidentical patterns provided with a displacement, and a depth of eachsurface tile of the object 130 is obtained by detecting positionalrelationships between the two identical patterns provided with adisplacement.

In one embodiment, the transparent substrate 280 may be replaced with alight valve. The term “light valve”, which is commonly known in theprojector industry, refers to individually-addressed optical units of aspatial light modulator. The spatial light modulator includes multipleindividually-addressed optical units arranged as a one-dimensional or atwo-dimensional array. Each optical unit can be individually addressedby optical or electrical signals to alter its optical properties throughvarious physical effects (e.g., Pockels effect, Kerr effect,photoacoustic effect, pagneto-optic effect, self electro-optic effectand photorefractive effect). Therefore, the multiple individuallyaddressed optical units may modify incoming light beams and output imagebeams. The optical units may be, for example, micro mirrors or liquidcrystal cells, and the light valve may be a digital micro-mirror device(DMD), a liquid-crystal-on-silicon panel (LCOS panel) or a transmissivetype LCD panel. Further, the transparent substrate 280 may be a mask ora projection slide.

FIG. 8 illustrates a pattern generation device according to anotherembodiment of the invention. In FIG. 8, identical components are denotedby the same numerals as in the above embodiments and their descriptionsprovided above will not be repeated here. The pattern generation deviceof this embodiment is different to the pattern generation device 410 inthat the light source 200 and the transparent substrate 280 providedwith a pattern are disposed on a lateral side of an HPDLC cell 210 d.Therefore, a light beam L from the light source 200 first passes throughthe transparent substrate 280 containing a pattern (not shown) to beconverted into an image beam with the pattern, and then the image beamwith the pattern is bent by the HPDLC cell 210 d at an angle of about 90degrees and further incident to the HPDLC cell 210 a. The subsequentpropagation path of the image beam is similar to the above embodimentsand thus is not repeatedly described here.

FIGS. 9A and 9B illustrate a pattern generation device according toanother embodiment of the invention. In FIGS. 9A and 9B, identicalcomponents are denoted by the same numerals as in the above embodimentsand their descriptions provided above will not be repeated here. Thepattern generation device in this embodiment is different to the patterngeneration device 310 in that the holographic optical element 250 isreplaced with a diffractive optical element (DOE) 295. As shown in FIGS.9A and 9B, since two different deflection angles α1 and α2 can be formedby controls of multiple switches 230 and deflection of the HPDLC cells210, a displacement between two identical patterns projected by the DOE295 onto the object 130 can be produced. Therefore, the image of theobject 130 captured by the image pick-up device 120 may include twoidentical patterns provided with a displacement, and a depth of eachsurface tile of the object 130 is obtained by detecting positionalrelationships between the two identical patterns provided with adisplacement.

According to the above embodiment, a pattern generation device havinglow power dissipation and low fabrication costs is provided, and thepattern generation device may provide periodic patterns and morecollimatable light beams to expand applications of structured light.

Though the embodiments of the invention have been presented for purposesof illustration and description, they are not intended to be exhaustiveor to limit the invention. Accordingly, many modifications andvariations without departing from the spirit of the invention oressential characteristics thereof will be apparent to practitionersskilled in this art. For example, the power transmission may be achievedby direct contact, indirect contact (via rigid or non-rigid intermediateobjects) or actions at a distance (such as a magnetic force). Further, aconnection between two elements is not limited to a direct direction andmay be alternatively realized by the use of an intermediate object, suchas a movable mechanical element, a controlling mechanical element, or aconnection mechanical element, without influencing the powertransmission. Therefore, unless limited otherwise, the terms“connected,” “coupled,” and “mounted” and variations thereof herein areused broadly and encompass direct and indirect connections, couplings,and mountings. It is intended that the scope of the invention be definedby the claims appended hereto and their equivalents in which all termsare meant in their broadest reasonable sense unless otherwise indicated.

What is claimed is:
 1. A pattern generation device, comprising: a lightsource; a first holographic polymer dispersed liquid crystal (HPDLC)cell disposed downstream of a light path of the light source andcontaining a first phase modulation pattern; and a second HPDLC celldisposed downstream of a light path of the first HPDLC cell andcontaining a second phase modulation pattern.
 2. The pattern generationdevice as claimed in claim 1, further comprising a power supplyelectrically connected to the first HPDLC and the second HPDLC.
 3. Thepattern generation device as claimed in claim 2, wherein, when the powersupply does not supply a voltage to the first HPDLC cell, the firstHPDLC cell is in a diffracting state and a light beam travelling throughthe first HPDLC cell is converted into an image beam with an imagepattern in correspondence with the first phase modulation pattern. 4.The pattern generation device as claimed in claim 2, wherein, when thepower supply does not supply a voltage to the second HPDLC cell, thesecond HPDLC cell is in a diffracting state and a light beam travellingthrough the second HPDLC cell is converted into an image beam with animage pattern in correspondence with the second phase modulationpattern.
 5. The pattern generation device as claimed in claim 1, whereinthe light source is a laser, a laser diode, an LED, an OLED, avertical-cavity surface-emitting laser, an edge-emitting laser, a bulb,or a light-emitting unit capable of emitting thermal-spectrum radiation.6. The pattern generation device as claimed in claim 1, wherein thelight source emits a light beam, and the light beam forms a prescribedimage pattern on an image plane.
 7. The pattern generation device asclaimed in claim 1, wherein the pattern generation device is integratedin a depth mapping system, and the depth mapping system comprises animage pick-up device and a calculation unit.
 8. A pattern generationdevice, comprising: a light source; a first grating switchable between anon-diffracting and a diffracting state and disposed downstream of alight path of the light source; a second grating switchable between anon-diffracting and a diffracting state and disposed downstream of alight path of the first grating; and a holographic optical elementdisposed downstream of a light path of the second grating, and theholographic optical element encoding a first phase modulation pattern incorrespondence with a first image pattern and a second phase modulationpattern in correspondence with a second image pattern.
 9. The patterngeneration device as claimed in claim 8, further comprising a powersupply electrically connected to the first grating and the secondgrating.
 10. The pattern generation device as claimed in claim 9,wherein, when the power supply supplies a voltage to the first gratingand the second grating, the first grating and the second grating are inthe non-diffracting state, and a light beam travels through the firstgrating and the second grating in a substantially straight direction.11. The pattern generation device as claimed in claim 9, wherein, whenthe power supply does not supply a voltage to the first grating and thesecond grating, the first grating and the second grating are in thediffracting state, a light beam incident to the first grating isdeflected by the first grating at a first angle, and the light beamincident to the second grating is deflected by the second grating at asecond angle different to the first angle.
 12. The pattern generationdevice as claimed in claim 8, wherein the light source is a laser, alaser diode, an LED, an OLED, a vertical-cavity surface-emitting laser,an edge-emitting laser, a bulb, or a light-emitting unit capable ofemitting thermal-spectrum radiation.
 13. The pattern generation deviceas claimed in claim 8, wherein the light source emits a light beam, andthe light beam forms a prescribed image pattern on an image plane. 14.The pattern generation device as claimed in claim 8, wherein the patterngeneration device is integrated in a depth mapping system, and the depthmapping system comprises an image pick-up device and a calculation unit.15. A pattern generation device, comprising: a light source; a lightvalve containing a pattern disposed downstream of a light path of thelight source; a first grating switchable between a non-diffracting and adiffracting state and disposed downstream of a light path of the lightvalve; a second grating switchable between a non-diffracting and adiffracting state and disposed downstream of a light path of the firstgrating; and a projection lens disposed downstream of a light path ofthe second grating.
 16. The pattern generation device as claimed inclaim 15, wherein, when a voltage is applied to the first grating andthe second grating, the first grating and the second grating are in thenon-diffracting state and the light beam travels through the firstgrating and the second grating in a substantially straight direction.17. The pattern generation device as claimed in claim 15, wherein, whenno voltage is applied to the first grating and the second grating, thefirst grating and the second grating are in the diffracting state, alight beam incident to the first grating is deflected by the firstgrating at a first angle, and the light beam incident to the secondgrating is deflected by the second grating at a second angle differentto the first angle.
 18. The pattern generation device as claimed inclaim 15, wherein the light valve is a digital micro-mirror device, aliquid-crystal-on-silicon panel, a transmissive type LCD panel, atransparent substrate, a mask or a projection slide.
 19. The patterngeneration device as claimed in claim 15, wherein the light source is alaser, a laser diode, an LED, an OLED, a vertical-cavitysurface-emitting laser, an edge-emitting laser, a bulb, or alight-emitting unit capable of emitting thermal-spectrum radiation. 20.The pattern generation device as claimed in claim 15, wherein the lightsource emits a light beam, and the light beam forms a prescribed imagepattern on an image plane.